Cerbo GX Installation

Table Of Contents
For 12 V battery banks/systems the IMT Si-RS485 series solar irradiance sensor range may be powered directly from the battery
bank and will continue to operate down to minimum voltage of 10.5 V (as measured at the sensor, account for voltage drop in the
cable).
For detailed wiring/installation notes and specifications refer to the IMT Si-RS485 series solar irradiance sensor 'Quick Reference
Guide' and Victron RS485 to USB interface cable ‘Datasheet’.
To ensure signal integrity and robust operation, particularly ensure that;
Extension cabling complies with the minimum cross-sectional area specifications in the related table - dependent on DC supply
voltage and cable length
Extension cabling has appropriate shielding and twisted pair cores
The original cable attached to the Victron RS485 to USB interface is reduced to a maximum length of 20cm in installations
where the total cable length is over 10m or there are installation/site specific interference issues – in this case appropriate/high
quality cabling should be used for the entire cable length, rather than only for the extension length
Cabling is installed separated/away from the main DC or AC power cabling
All wiring is properly terminated (including unused wires) and properly isolated from weather/water ingress
The sensor housing is not opened or tampered with during installation - as sealing integrity will be compromised (and warranty
void)
The IMT Si-RS485TC series solar irradiance sensor includes internal Galvanic Isolation (up to 1000V) between power supply and
RS485 Modbus circuits, accordingly the non-isolated Victron RS485 to USB interface is suitable for most installations.
However, if an isolated RS485 to USB interface is preferred the only compatible device is Hjelmslund Electronics USB485-
STIXL (any others type will not be recognised by the GX device).
Multiple Sensors
It is possible to connect multiple IMT Si-RS485 series solar irradiance sensors to a common Victron GX device, however a
dedicated Victron RS485 to USB interface is required for each individual unit.
Multiple units cannot be combined on a single interface (as this is not supported by the related Venus OS software).
Configuration
There is normally no need for any special/additional configuration – the default ‘as shipped’ configuration is compatible for
communication with a Victron GX device.
However, in cases where the IMT Si-RS485 series solar irradiance sensor has been previously used in another system and/or the
settings changed for any reason, it is necessary to restore the default configuration before further use.
To revise the configuration, download the IMT 'Si-MODBUS-Configuration software tool'. Follow the instructions in the IMT ‘Si
Modbus Configurator Documentation’. and check/update the following settings:
MODBUS Address: 1
Baud Rate: 9600
Data Format: 8N1 (10 Bit)
For further support related to configuration of the IMT Si-RS485 Series irradiance sensors please contact IMT Solar directly.
User Interface - GX Device
Upon connection to the Victron GX device and power up the IMT Si-RS485 Series irradiance sensor will be automatically
detected within a few minutes and appear in the 'Device List' menu.
Cerbo GX Manual
Page 10 Installation